The elements of eloquence is the best resource i’ve found on rhetorical devices. It helps that the author is witty. Wodehouse witty, even.

Rhetoric doesn't excuse the need to address your customer's underlying needs. First say it straight, then say it great.

Rhetoric helps communicate a specific message. But brands still need to have a consistent, differentiated place in your mind across messages – that's something archetypes and cultural branding help with. Follow the rabbit hole – this stuff is fascinating and useful.